Controlled reading device

ABSTRACT

A controlled reading method and apparatus useful in improving a person&#39;&#39;s ability to view and to comprehend reading material in line by line sequence wherein each line is unveiled and occluded to view in segments in the direction of reading from the beginning of the line to the end of the line with the beginning and central segments being scanned and occluded at controlled rates of speed which may be related to the person&#39;&#39;s reading ability and with the beginning segment being unveiled at a relatively more rapid rate and the terminal segment being occluded at a relatively more rapid rate whereby the transition from the end of each line to the beginning of the succeeding line is more rapid and a relatively greater length of reading material is more rapidly exposed at the beginning of the next line to facilitate recognition. The unveiling scanning and occluding of the segments of the line may be accomplished by means of a movable mask or shutter with an aperture shiftable with respect to each line so as to scan the line from beginning to end with the said aperture being in the form of an elongated or helical slot arranged at an angle with respect to the length axis of the line to be scanned with the initial portion of the slot being disposed in a downward direction and the terminal portion in an upward direction with respect to the axis of the line and with the leading and trailing edges of the central segment of the slot and the trailing edge of the initial segment of the slot being disposed at relatively greater angles to said length axis of the line than the remaining edges of the slot and with the trailing edge of the terminal segment and the leading edge of the initial segment of the slot being disposed at a relatively lesser angle to the length axis of the line. The lines of reading material may be formed on a film strip mounted on a stick slide having ratchet-like notches formed along the sides of the slide and advanced line by line by means of mechanism actuated by operation of the shutter. Various controls are provided whereby the reading range can be varied, the film stopped at any line, moved backwards to repeat a line, or advanced manually, or lines of material can be projected tachistoscopically.

United States Patent [1 1 Taylor 1 Sept. 11, 1973 CONTROLLED READINGDEVICE [76] Inventor: Stanford E. Taylor, Hawk Dr., Lloyd Harbor, NY.

[22] Filed: June 1, 1972 [21] Appl. No.1 258,612

Primary Exa min erWm. H. Grieb [5 7] ABSTRACT A controlled readingmethod and apparatus useful in improving a persons ability to view andto comprehend reading material in line by line sequence wherein eachline is unveiled and occluded to view in segments in the direction ofreading from the beginning of the line to the end of the line with thebeginning and central segments being scanned and occluded at controlledrates of speed which may be related to the persons reading ability andwith the beginning segment being unveiled at a relatively more rapidrate and the terminal segment being occluded at a relatively more rapidrate whereby the transition from the end of each line to the beginningof the succeeding line is more rapid and a relatively greater length ofreading material is more rapidly exposed at the beginning of the nextline to facilitate recognition. The unveiling scanning and occluding ofthe segments of the line may be accomplished by means of a movable maskor shutter with an aperture shiftable with respect to each line so as toscan the line from beginning to end with the said aperture being in theform of an elongated or helical slot arranged at an angle with respectto the length axis of the line to be scanned with the initial portion ofthe slot being disposed in a downward direction and the terminal portionin an upward direction with respect to the axis of the line and with theleading and trailing edges of the central segment of the slot and thetrailing edge of the initial segment of the slot being disposed atrelatively greater angles to said length axis of the line than theremaining edges of the slot and with the trailing edge of the terminalsegment and the leading edge of the initial segment of the slot beingdisposed at a relatively lesser angle to the length axis of the line.The lines of reading material may be formed on a film strip mounted on astick slide having ratchet-like notches formed along the sides of theslide and advanced line by line by means of mechanism actuated byoperation of the shutter. Various controls are provided whereby thereading range can be varied, the film stopped at any line, movedbackwards to repeat a line, or advanced manually, or lines of materialcan be projected tachistoscopically.

16 Claims, 9 Drawing Figures PATENTEDS'EH I913 3.757. 432

SHEEI 1 [IF 5 PATENTEUSEPI new SHEEI 2 BF 5 PATENTED "973 SHEET 3 [IF 5PATENTEDSEPI i191;

SHEET t UP 5 CONTROLLED READING DEVICE BACKGROUND OF THE INVENTION It isan object of this invention to provide an improved controlled readingdevice and method wherein the terminal portion of a line being unveiledand occluded in segments in the direction of reading is occluded at arelatively more rapid rate and the initial portion of the succeedingline is unveiled at a relatively more rapid rate whereby transition fromthe end of one line to the beginning of the next line is more rapid andrecognition of the beginning of the next line is facilitated.

It is a further object to provide a device in which the film strip ismounted on a semi-rigid stick slide which is fed through the projectorby gravity to give a more rapid line to line indexing, a means by whichthis reading material can be pulled up manually in order to repeatsegments of material, and a means whereby film material can be moreeasily handled and engaged with less film damage and wear.

It is a further object to provide a tachistoscopic feature whichpresents high speed exposures of words, symbols, pictures or other likematerial.

It is a further object to provide for processing training otherwiseknown as continuous tachistoscopic projection in which words of a storyare projected, one word per line, at rates much higher than those usualfor left to right reading.

It is a further object to provide a momentary control mechanism for thedevice to pennit stopping the film at any line should a teacher wish todiscuss the content.

It is a further object to provide a filmstrip stick slide for the devicewhich permits two rows of lines of information to be positionedside-by-side with one row right side up and the other row upside downwhereby reversal of the slide allows showing the second row of lines,thus providing a more condensed and compact film form.

BRIEF DESCRIPTION OF THE DRAWING Other objects and advantages willbecome apparent from the following description which is to be taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of the device of the present invention;

FIG. 2 is a side view partially in section;

FIG. 3 is a top view partially in section;

FIG. 4 is a front view partially in section;

FIG. 5 is an exploded perspective view of some of the main elements ofthe device;

FIG. 6 is a fragmentary view of the film strip and helix;

FIG. 7 is a view of the form of slot for the helix;

FIG. 8 is an enlarged view showing how the slot for the helix is cut inthe helix tube; and

FIG. 9 is a front view of the plate sliding mask of the device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly tothe drawings, there is shown in FIG. 1 the device embodying the presentinvention. The projection system and all other elements of the deviceare mounted above base plate 10 and enclosed within a cover or casing 11secured to the base. However, if a projection lamp of 12 volts is used,a transformer will be necessary, which transformer can be mountedunderneath the base plate 10. If a 1 10 volt lamp is used no transformerwill be required. For convenience and ease of removal of such cover toget at the various parts, it has been found advantageous to form thecover of at least two parts, but this can be varied as preferred.

Forming a part of the base plate 10 is an integral mounting bracket 12into which is threaded a hand screw member 13. If a transformer ismounted under the base plate 10, the length of the bracket 12 can beextended to provide room above the screw member 13. Such bracket andscrew member permit the device to be easily clamped onto all of thelearning stations being provided today for learning laboratories,learning resource centers, communication laboratories, etc. This avoidsthe necessity of providing a special tablet or extension to accommodatethe reader. A bolt can be substituted for the screw member so that thereader can be bolted to a booth to prevent easy removal. If freestanding use is desired, this device can likewise be bolted to a tripod,metal plate or similar stand.

The projection system, shown in FIG. 2, includes a projection lamp 14, acondensing lens system 15, and

. vided with a ventilator 11a to permit the release of the heat whichwill be generated by the lamp.

Also mounted on the base plate 10 is an electric gear motor 20 whichdrives the helix shaft 21 through motor pulleys 22 and 22a, belts 23 and23a and helix pulleys 24 and 24a (FIG. 5). The shaft of the motor has aslidable sleeve over it so that a key can be moved by means of knob 20ato engage a slot in either pulley 22 or 22a. In this manner the helixshaft can be driven at a 1:1 or 1:4 ratio. Such speed shifter isconventional and is not shown in detail. Secured to the shaft 21 areknob 25 with pin 25a for manual rotation of the shaft, cylindrical helixmember 26 provided with a helical slot 27 extending diametrically acrossthe cylindrical member, cam 28, and brake member 29 provided with a pin30 which serves as a brake as hereinafter described. One end of theshaft 21 is mounted on a side of the device above the base plate withthe shaft passing through the casing and the knob 25 accessible from theoutside of the devive. The brake member 29 at the other end of the shaft21 passes through an L-shaped mounting block 31 secured to the internalcross-frame of the device with the pin 30 extending beyond the block sothat it can rotate freely. A pivoted spring plate 32 is secured to theinternal cross-frame by pivot 33. The plate 32 projects through the topof the casing and is provided with a handle portion 34 which permits theplate to be moved into the path of the pin 30 thereby braking the shaft21 and preventing it from rotating. When the plate 32 is pivoted so thatit is out of the path of the pin 30, the shaft 21 is free to rotate.

In addition, pressing on pin 250 will cause pin 30 to override spring 32and the shaft will move through one complete revolution, providing rapidline changes wich can be used to provide tachistoscopic exposures.

The block 31 is provided with horizontal slots 31a and 31b to receiveL-shaped slide members 38 and with vertical slot 31C to receive pawlmember 39. The pawl member 39 is exaggerated in size in FIG. 5 to showthe details more clearly. Such members are retained within the slots byplate 40 secured to the block 31. The pawl member 39 is further retainedby a pin which passes through hole 40a in the plate and hole 39a in thepawl member so that the pawl member is free to rotate through a smallarc. The pawl member 39 also passes through rectangular slots 38a in theslide members 38. The end leg of each slide member 38 is provided with ascrew 38b which can be adjusted to serve as a stop to limit the movementof the slide member. The pawl member 39 is so positioned that the cam 28rides against the pawl 39b of the pawl member. Springs 41 and 42 areattached at one end to the pawl member 39 and at the other end to theend legs of the slide members 38. Another spring 43 is attached at oneend to the end of the pawl member 39 and at the other end to the frameso that the lower slide member 39 is normally projecting beyond the faceof the block 31 at the time when the depressed portion of the cam 28 isresting against the pawl 39b. Upon further rotation of the cam theraised portion rides against the pawl 39b causing the pawl member 39 torotate. This causes the lower slide member 38 to retract and the upperslide member 38 to project beyond the face of the block 31.. It will beunderstood that other means may be employed to attain the reciprocatingmovement of the spring-loaded slide members 38. For example, pivotingpawls or flexing spring members may be used to successively retract andproject against the stick slide as hereinafter described. Such pawls andspring members would likewise be engaged by the rotating cam 28.

The internal cross frame of the device is provided with slot 44 adaptedto receive a stick slide 45 to which the film 46 is affixed. The stickslide 45 may be made of plastic, metal or like material. The film may beattached to the slide in any conventional manner, for example, adhesive,transparent tape, lamination, projections matching the slots in thefilm, between welded plastic members, or combinations thereof.Furthermore, it is possible to sensitize the stick and print on thestick optically. Such slide 45 has a series of ratchet teeth 45:: and45b on each side. The respective ratchet teeth 45a and 45b point inopposite directions so that the slide may be reversed. The lower edge ofthe ratchet teeth, which are in operative position, are disposed atapproximately right angles to the vertical axis. The slide is insertedin the slot so that the teeth 45a, which point downward, are positionedon the side of the device where the slide members are located. Suchteeth 45a are aligned with the slide members 38 so that either the upperslide member or the lower slide member is pressing against the slidebeneath a tooth and holding the stick slide. With the depressed portionof cam 28 resting against the pawl 39)) the lower slide member projectsbeneath a tooth of the stick slide. When the shaft 21 rotates, theraised portion of the cam rides against the pawl 39b causing the pawlmember 39 to rotate. Such rotation of the pawl member causes the lowerslide member 33 to retract and release the tooth above it. The stickslide drops by gravity but is stopped from moving more than one notch bythe upper slide member which has been projected forward beneath anothertooth of the stick slide by the further rotation of the pawl member. Thecontinued rotation of the shaft 21 will, in this manner, move the stickslide downward line-by-line. The stick slide can be pulled up manuallyto repeat any segments of the material on the film. it is possible toadvance the film manually by rotating the knob 25. If the teacher wantsto stop the projector, as in the case of vocabulary or readinessactivity, she would simply hold the knob 25 attached to the shaft 21,thereby causing the belts to slip. in this way she would hold thematerial in a stationary manner until she was ready to release the knob,which would allow automatic projection to continue. As heretoforepointed out, the movement of the film can also be stopped by moving thehandle portion 34 of the plate 32 and applying the brake against theshaft 21. This might be desirable if the teacher wishes to discuss thecontent of any line on the film.

An alternate method is to drive the stick slide by use of the filmperforations in which case the ends of the slide members 38, flexingspring members or like means will be shaped to engaged the filmperforations and move the slide and film in a line-by-line manner. Insuch case the ratchet teeth 45a and 45b can be eliminated.

The cooperation between the lever 32 and the speed shifter provides atachistoscopic control as mentioned earlier. The purpose of such controlis to present single words, members, phrases or symbol material in atachistoscopic manner at speeds that will not permit the reader to movehis eyers. Such training develops perceptual accuracy in the student. Asthe student attempts to apprehend and retain these brief exposures, helearns to see with greater rapidity, accuracy and orderliness. Thetachistoscopic effect is accomplished by applying the brake (springplate 32) as described above, which stops rotation of the shaft 21 andforward movement of the stick slide. To make a tachistoscopic exposure,the teacher taps the pin 25a on the knob 25 which overcomes the springplate 32 and allows the shaft to make one revolution at which time it iscaught again. During this interval of one rotation the stick drops to alower position presenting visual material and then drops a second timeremoving the visual material. The duration of the time of exposure orthe time the visual material is presented is dependent on the setting ofthe speed control 4'7.

Pushing on or pulling speed selection knob 200 as stated previouslychanges the projection rate. The 1:1 speed range is used for regularreading while the lz4 speed range is used for processing training, oftenreferred to as continuous tachistoscopic projection because of therelatively short duration during which each line of material on the filmremains in the projection aperture. The purpose of this mode of trainingis to present single words, placed centrally on each projection line, atrates so rapid as to prevent the reader from refixating or making asecond eye movement during the exposure of each word and thus to effectreading rates 25 percent to 100 percent faster than the rate ofpresentation normally used in left to right reading training. A goal ofprocessing training is to remove the physical limitation imposed by thevisual functional mechanism of a reader's eyes and allow him toconcentrate all his energies on the perceptual act of seeing andassimilating words as continuous sequences of words or thoughtprogressions.

The film 46 mounted on the stick slide 45 bears reading material whichis greatly reduced in size thus permitting a considerable amount ofprint in a small amount of film, for example, 320 lines of print in some8 inches of film. A greater reduction of copy is considered possiblewithout affecting the reading. The slide format here described has theadvantage of being simpler in operation than any cassette load byeliminating the take-up or rewind complications and of providing aconsiderable amount of protection for the film. The small amount of filmemployed and the ease of mounting the film on the slide providesconsiderable savings in softwear production over conventional filmstrippackaging and over cartridge packaging.

The film strip contains two rows of reading material in side-by-siderelationship (FIG. 6). As the film strip is fed into the device, onlythe row on one side is aligned with the projection system. When this rowhas been completed, the stick slide bearing the film strip is inverted,with the same side facing the projection system, bringing the other rowof reading material on the film into alignment with the projectionsystem. By such inversion of the stick slide, the teeth 45b, which werepointing upward, are now pointing downward so that they will engage theslide members 38 as heretofore described.

The diametrically extending helical slot 27 in the cylindrical helixmember 26 is interposed to rotate in the path of light between theprojection system and the lens. Such slot, shown in perspective anddevelopment in FIGS. 6, 7 and 8 is milled so that the slot extendsapproximately l90 around member or tube 26 which member is of tubularform and actually consists of a pair of similar slots formed indiametrically opposite relationship in the cylindrical member. In theprocess of milling, the helical slot 27 may be milled diametricallythrough the tube cutting the slot 27 in the opposite sides of the tubeat the same time. It will be seen, therefore, that since the slotextends diametrically through member 26, that as member 26 rotates therewill be an open passage for projection light through said member at alltimes, but due to the helical form of the slot the opening will appearto move across the field of projection.

The rotation of tube 26 allows the projection of portions of the line tobe read in sequence progressively across the screen and may expose orallow projection of any desired portion of the line, but approximatelyone-third of the line is exposed at a time. The effect is that of aslowly moving slot of light uncoveringthe line of print and when theslot has reached the extreme end of the line, a new line of material ismoved into place. The slot disappears at the end of each line andreappears on the left for the new exposure. The rate at which this slotmoves and correspondingly the lines exposed per minute can be regulatedas desired within reason, such as from 10 lines per minute toapproximately 600 lines per minute.

The present system improves a persons ability to view reading materialin line-by-line sequence which completely displays a line of at leastfive words in segments across the line. The greater portion of the linebeing scanned is occluded and a first segment of the line consisting ofone full word or a portion thereof is unveiled. The last segment of theline being scanned consists of at least a portion of the last word ofthe line so that transition from the end of the line to the beginning ofthe next line will present to the reader no less print than theequivalent of his average span of recognition. As stated, thesegmentation of an individual line can be broken down into anycombination of elements. For example, representative of a satisfactoryarrangement of segmentation would be a first segment comprisingapproximately 31 percent of the line, a central segment comprisingapproximately 54 percent of the line and a final segment comprisingapproximately 15 percent of the line.

The shift to each new line of print is positioned correctly by thenotches on the stick slide, as described above. Because the stick slideuses a gravity feed principle, the indexing from line to line is morerapid than conventional gear or sprocket arrangements. This has theadvantage of allowing the print to remain stationary for a greateramount of time, up to the time each line of print is completelyoccluded. As the print at the end of each line of print vanishes fromview, the reading material would be indexed so quickly as to appearmotionless by the time any new print is exposed at the beginning of eachnew line of print.

Interposed between the stick slide 45 holding the film and the helixshaft 21 is a plate sliding mask 35 which is inserted in a slot in thetop of the casing.'This mask is provided with a handle portion 36 sothat it can be raised or lowered by hand. The mask has a series ofapertures 37a, 37b, 37c and 37d to permit viewing across the full lineof print or only portions of such line. It will be understood that thesize, position and number of apertures can be varied to expose anydesired portion of a line.

In my U.S. Pat. No. 2,745,313 covering a Controlled Reading Projectorthere is shown a helix with a slot having parallel straight sides andcircular ends so that it is uniform throughout, as shown by the dottedline A in FIG. 8. The slot of the present invention has been recut inthe form shown by the line B in FIGS. 7 and 8. To obtain the form shownby the Line B, the tube is milled along three lines C1, C2, and C3 tothe width shown by the lines D1, D2 and D3 representing the trailingedges along one side and lines El, E2 and E3 representing the leadingedges along the opposite side. The slot is then milled again to removeshaded portions F and G which gives the ultimate slot addition width atthe two ends of the slot and modifies the angles of the edges. The finalslot defined by the line B has a central portion angularly positionedaround the tube 26 with the first and second end portions tiltedupwardly 'and downwardly toward the axis of the tube to give the slot anelbow-like or flattened S configuration. The slot is widened along oneedge at the joint between the central portion and the first end portionand also along the opposite edge at the joint between the centralportion and the second end portion. Thus, the cylindrical member 26forms a shutter or mask having an elongated aperture of helical formwhich serves to unveil each line to view in segments from the beginningof the line to the end of the line. The helical aperture is an elongatedslot at least as long as the lines to be scanned and in use is arrangedat at an angle with respect to the length axis of the line with theinitial portion of the line being disposed in a downward direction andthe terminal portion in an upward direction with respect to the axis ofthe line and with the leading and trailing edges of the central segmentof the slot and the trailing edge of the initial segment of the slotbeing disposed at a relatively greater angle to the length axis of theline being scanned than the remaining edges of the slot so that thecentral and initial segments are scanned and occluded at controlledrates of speed which may be related to the persons reading ability. Theleading edge of the initial segment of the slot and the trailing edge ofthe terminal segment of the slot are disposed at relatively lesserangles whereby the terminal segment of the line is occluded and theinitial segment is unveiled at relatively more rapid rates.

The helix with this recut slot will expose print more rapidly at thebeginning of each line as well as terminate the scanning at the end ofeach line more rapidly. As a result, a reader will be prompted toexecute a return sweep at an earlier point at the end of each line ofprint and upon effecting his return sweep to the beginning of each newline of print the reader will always find an amount of print exposedthat is appropriate for his span of recognition. To accomplish this, theangle of the lead edge of the initial portion of the helix has beenmodified so that illimination or unveiling of the print occurs at afaster rate at the beginning of each line of print, the following edgemaintains a fairly consistent rate of scanning and occlusion untilapproximately the last one-seventh of the line, whereupon the occlusionof the line of print is accelerated. Initial testing of the oldillusionwith the new indicates that this new helix presents lines ofprint in a manner that conforms more closely to a readers usualocular-motor behavior and recognition requirements, thus providing areader with a more satisfying perceptual experience.

In the redesign of the helix, a prime consideration was that the readersshould be provided with no less print than the equivalent of theiraverage span of recognition when returning to the beginning of a newline of print and at any time during their excursion across the line ofprint and be prompted to execute a return sweep more rapidly at theconclusion of each line of print. This is in contrast to the helix ofU.S. Pat. No. 2,745,313 where a reader, with the projection rate setjust slightly faster than his usual reading rate, could return to thebeginning of a new line of print to find either no print awaiting him orless print that he typically requires in terms of his average span ofrecognition.

The redesigned helix of the present invention provides one means foraccelerating the unveiling of print at the beginning of each line ofprint and a more rapid occlusion of print at the end of each line asheretofore described. However, it will be understood that this can beaccomplished in other ways, such as (1) varying the rate of rotation ofthe mask, picture, or. occluding means by a change of voltage or achange in the nature of the energizing force during scanning; (2)driving the mask or occluding means with a variable pitch cam; (3) usingan external helix to mask or occlude the scanning; and (4) using lightdeflecting means designed to change the rate of the reflectionrefraction of the transmission of light.

Readers will vary in their ocular-motion behavior for a number ofreasons, but some of the factors would center primarily on theindividual reactions of various readers to the left-to-right scanningillusion and the manner in which they return to each new line of print.Such individual reactions would be based on:

A. The cue(s) the reader responds to that cause him to initiate a returnsweep. Readers will vary in the type of cue(s) they respond to.Following are a few:

1. The obliteration of the reader's fixation point by the following edgeof the helix (the earliest cue) 2. The reduction of visible print to apoint that is less than the average span of recognition of the reader 3.The upward movement of print 4. The total elimination of the print cues(the latest cue).

B. Lag Time, or the interval of time the reader delays before executinghis return sweep. Readers will remain fixated for varying lengths oftime following a cue to execute a return sweep based on:

1. Their tendency to maintain their usual duration of fixation 2. Theamount of processing time they require 3. An inertia factor that resultsfrom a change of ocular-motion direction.

C. Return sweep interval, or the amount of time it physically takes fora reader to swing back from his last fixation to an initial fixation ona new line of print. This interval of time will typically range between0.03 seconds and 0.045 seconds, the longer interval of time beingrequired to execute a longer return sweep and in instances where areader's motility is less well developed.

D. Vergence and Accommodation time would be that interval of timerequired to fuse in a binocular manner during the first fixation and toaccommodate so that print can be seen clearly. Generally, this intervalof time ranges between 0.01 seconds and 0.02 seconds for readers with nospecial visual anomalies.

E. Individual response to the left-toright scanning illusion. Readerswill respond in a rather individual manner to the scanning illustion ofthe controlled reading device based on the following differences:

1. Some readers will be able to sense and adjust to the average amountof viewing time permitted by the moving slot. A reader who is thisresponsive will typically execute his usual number of fixations whilereducing his duration time. The more accomplished a reader is in thisrespect, the more similar in length will be his durations of fixation.

2. The tendency of some readers will be to persist in trying to maintaintheir habitual duration of fixation. These readers will vary more in thedurations they effect along a line of print. More often than not, theywill execute longer durations toward the beginning of a line of printthan at the end.

3. Some readers will tend to prolong their duration of fixation as they(a) decrease the number of fixations they make along a line of print,(b) as they consequently execute greater than usual excursions, and (c)because of the increased processing time they require as they attempt toassimilate more print with each fixation.

If the reader responded to the earliest possible clue, which thefixation point obliterated, and his lag time was a minimum 0.125 secs.and his return sweep was quite brief, 0.03 secs. and his vergence andaccommodation time was quite short, 0.01 secs., the amount of printprovided by the new helix of the present invention would be an amount inaccord with or in excess of the reader's average span of recognitionrequirements. On the other hand, the old helix design providedapproximately to percent less than the readers average span ofrecognition requirements.

In addition the new helix, by occluding end line of print more rapidly,prompts a reader to execute a return sweep at an earlier point in theline than did the old helix design and by so doing discourages allreaders to lag or delay less at the conclusion of each line and to bemore responsive to the conclusion of a line of print.

Connected to the gear motor 20 is a potentiometer or speed controller 47provided with a numbered dial on the outside of the casing so that themotor can be set at the desired speed. The device is thus capable toproviding between 10 and 600 lines per minute. The speed shifter,heretofore described, allows for two speed ranges; a reading rate rangeextending slightly beyond 750-800 words per minute as well as a rangeextending well beyond 800 words per minute that can present prints atrates up to four times that usual for a reading range in order toprovide for skimming or processing training. in addition there is a trimpotentiometer 48 or voltage regulator to compensate for the supplyvoltage variation. This assures that the reading rates on thepotentiometer will be accurate.

The controlled reading device of the present invention makes use ofprojection as a means of presenting the reading material on a front orrear projection screen, and the material to be projected is in filmstrip 46 form with every two lines of material corresponding to a notchon the stick slide with an average strip comprising title, code and 320lines of reading and viewing material to be projected, so that each lineof material to be projected may be aligned with the projection aperturesuccessively. Since two lines of viewing material correspond to a notchon the stick slide, when one slide member or like means is engaging anotch, the other slide member is positioned between two notches. Thus,as the one slide member retracts and the other projects to engage anotch the stick slide exposes the next line but only moves one half thedistance between notches.

In the operation of the device, the instructor determines the speed ofoperation of the device, that is, the number of lines per minute to beexposed or projected by adjustment of the speed controller 47 and theslide stick, on which is mounted the film strip to be projected, isinserted into the projector. The slide member 38 stops the stick slidewhen it engages the first notch of the slide. The projector and themotor are turned on and the device is in automatic operationby means ofthe motor 20 which operates shaft 21, helix member 26 and slot 27, asdescribed above.

The use and purpose of the controlled reading device should be apparentfrom the foregoing description. Thus, the aforenoted objects andadvantages are most effectively attained. Although the preferredembodiment of the invention has been disclosed and described herein, itshould be understood that this invention is in no sense limited therebyand its scope is to be determined by that of the appended claims.

Thus as previously indicated, the specific mechanism for obtaining themore rapid unveiling of the initial segment of the line and forobtaining more rapid transition from one line to another may be varied.In addition, under certain circumstances the more rapid occlusion of theend of each line may be omitted provided that the system provides for amore rapid unveiling of the initial portion of the succeeding line.

I claim:

1.. In a method useful in improving a persons ability to view and tocomprehend reading material in line-byline sequence of the type in whichthe lines are separately exposed in timed sequence, the improvementwhich comprises:

unveiling and occluding each line to view in segments in the directionof reading from the beginning of the line to the end of the line withthe central segment being scanned and occluded at a controlled rate ofspeed which may be related to the persons reading ability and with theinitial segment being unveiled at a relatively more rapid rate than therate of the central segment whereby a relatively greater length ofreading material is more rapidly exposed at the beginning of thesucceeding line to facilitate recognition.

2. In a method useful in improving a persons ability to view andcomprehend reading material in line-byline sequence of the type setforth in claim 3 the improvement which comprises varying the rate ofscanning and occluding of the central segment so as to accommodate theviewing and recognition ability of different readers and simultaneouslyproportionally varying the rate of unveiling of the initial segment.

3. in a method useful in improving a persons ability to view and tocomprehend reading material in line-byline sequence of the type in whichthe lines are separately exposed in timed sequence, the improvementwhich comprises:

unveiling and occluding each line to view in segments in the directionof reading from the beginning of the line to the end of the line withthe central segment being scanned and occluded at a controlled rate ofspeed which may be related to the person's reading ability and with theinitial segment being unveiled at a relatively more rapid rate than therate of the central segment and the terminal segment of the line beingoccluded at a relatively more rapid rate than the rate of the centralsegment whereby the transition from the end of each line to thebeginning of the succeeding line is more rapid and a relatively greaterlength of reading material is rapidly exposed at the beginning of thenext line to facilitate recognition.

4. In a method useful in improving a person's ability to view andcomprehend reading material in line-byline sequence of the type setforth in claim 3 the improvement which comprises varying the rate ofscanning and occluding of the central segment so as to accommodate theviewing and recognition ability of different readers and simultaneouslyproportionally varying the rate of occluding of the terminal segment andthe rate of unveiling of the initial segment.

5. lln apparatus useful in improving a person's ability to view and tocomprehend reading material in line-by line sequence of the type havingmeans for separately exposing the lines in timed sequence, theimprovement which comprises:

a shutter mechanism for unveiling and occluding each line to view insegments in the direction of reading from the beginning of the line tothe end of the line said shutter mechanism having an aperture shiftablewith respect to each line so as to scan the line from beginning to endand configured so that the central segment is scanned and occluded at acontrolled rate of speed which may be related to the persons readingability and the initial segment is unveiling at a relatively more rapidrate than the rate of the central segment and a relatively greaterlength of reading material is more rapidly exposed at the beginning ofthe succeeding line to facilitate recognition.

6. In apparatus useful in improving a person's ability to view andcomprehend reading material in line-byline sequence of the type setforth in claim the improvement which comprises providing means forvarying the rate of scanning and occluding the central segment so as toaccommodate the viewing and recognition ability of different readers andfor simultaneously proportionally varying the rate of unveiling of theinitial segment.

7. In apparatus useful in improving a persons ability to view and tocomprehend reading material in line-byline sequence of the type havingmeans for separately exposing the lines in timed sequence, theimprovement which comprises:

a shutter mechanism for unveiling and occluding each line to view insegments in the direction of reading from the beginning of the line tothe end of the line said shutter mechanism having an aperture shiftablewith respect to each line so as to scan the line from beginning to endand configured so that the central segment is scanned and occluded at acontrolled rate of speed which may be related to the persons readingability and the initial segment is unveiled at a relatively more rapidrate than the rate of the central segment and the terminal segment ofthe line is occluded at a relatively more rapid rate than the rate ofthe central segment whereby the transition from the end of each line tothe beginning of the succeeding line is more rapid and a relativelygreater length of reading material is more rapidly exposed at thebeginning of the next line to facilitate recognition.

8. ln apparatus useful in improving a person's ability to view andcomprehend reading material in line-byline sequence of the type setforth in claim 7 the improve'ment which comprises providing means forvarying the rate of scanning and occluding the central segment so as toaccommodate the'viewing and recognition ability of different readers andfor simultaneously proportionally varying the rate of occluding theterminal segment and the rate of unveiling of the initial segment.

9. Apparatus useful in improving a persons ability to view andcomprehend reading material in line-by-line sequence of the type setforth in claim 7 in which the lines of reading material to be exposedare mounted on a generally vertically disposed slide having a row ofgenerally vertically disposed ratchet teeth and the apparatus isprovided with a generally vertically arranged opening to receive thesaid slide in alignment with the shutter, said apparatus also havingfeed mechanism including a pawl member for engaging said ratchet teethand having operating means synchronized with said shutter mechanism forreleasing and engaging successive teeth whereby the slide is feddownwardly by gravity with successive lines of reading material inalignment with the aperture.

10. Apparatus useful in improving a person's ability to view andcomprehend reading material in linebyline sequence of the type set forthin claim 7 in which the lines of reading material to be unveiled areformed in first and second parallel columns on a generally verticallydisposed slide with the second column being in inverted relationshipwith respect to the first column, said slide having a first row ofgenerally vertically disposed ratchet teeth for the first column and asecond generally vertically disposed row of ratchet teeth for the secondcolumn which in turn is arranged in inverted relationship with respectto the first row, and the said apparatus is provided with a generallyvertically arranged opening to receive the said slide in alignment withthe shutter with the first column of reading material being in alignmentwith the aperture when the slide is in one vertical position and thesecond column being in alignment with the aperture when the slide is inan inverted position, said apparatus having feed mechanism including apawl member for engaging the first row of ratchet teeth when the slideis in one vertical position and for engaging the second row of ratchetteeth when the slide is in inverted position and said apparatus havingoperating means for said pawl synchronized with said shutter mechanismfor releasing and engaging successive teeth in said respective rows ofratchet teeth whereby the slide is fed downwardly by gravity withsuccessive lines of reading material in the respective columns inalignment with the aperture.

1 1. In apparatus useful in improving a persons ability to view and tocomprehend reading material in line-byline sequence of the type havingmeans for separately exposing the lines in timed sequence, theimprovement which comprises:

a shutter mechanism for unveiling and occluding each line to view insegments in the direction of reading from the beginning of the line tothe end of the line said shutter mechanism being shiftable with respectto each line so as to cause the aperture to scan the line from beginningto end, the said aperture being in the form of an elongated slot atleast as long as the lines to be scanned and being arranged so that whenit is in operative position it is disposed at an angle with respect tothe length axis of the line being scanned with the initial portion ofthe slot being disposed in a downward direction and the terminal portionin an upward direction with respect to the axis of the line and with theleading and trailing edge of the central segment of the slot beingdisposed at a relatively greater angle to the length axis of the linebeing scanned than the hereinafter referred to edges of the slot so thatthe central segment of the line is scanned and occluded at a controlledrate of speed which may be related to the persons reading ability andwith the leading edge of the initial segment of the slot being disposedat a relatively lesser angle to the length axis of the line beingscanned whereby the initial segment is unveiled at a relatively morerapid rate than the rate of the central segment so that upon shifting ofthe apparatus from beginning to end of the line and then shifting of therelative position of the aperture with respect to a succeeding line arelatively greater length of reading material is more rapidly exposed atthe beginning of the succeeding line to facilitate recognition.

12. In apparatus useful in improving a persons ability to view andcomprehend reading material in line-byline sequence of the type setforth in claim 11, the improvement which comprises providing means forvarying the rate of speed for shifting of the shutter mechanism so as tovary the rate of scanning and occluding the central segment of the lineto accommodate the viewing and recognition ability of different readersand for simultaneously proportionally varying the rate of unveiling ofthe initial segment of each line.

13. In apparatus useful in improving a persons ability to view and tocomprehend reading material in line-byline sequence of the type havingmeans for separately exposing the lines in timed sequence, theimprovement which comprises:

a shutter mechanism for unveiling and occluding each line to view insegments in the direction of reading from the beginning of the line tothe end of the line said shutter mechanism being shiftable with respectto each line so as to cause the aperture to scan the line from beginningto end, the said aperture being in the form of an elongated slot atleast as long as the lines to be scanned and being arranged so that whenit is in operative position it is disposed at an angle with respect tothe length axis of the line being scanned with the initial portion ofthe slot being disposed in a downward direction and the terminal portionin an upward direction with respect to the axis of the line and with theleading and trailing edge of the central segment of the slot beingdisposed at a relatively greater angle to the length axis of the linebeing scanned than the hereinafter referred to edges of the slot so thatthe central segment of the line is scanned and occluded at a controlledrate of speed which may be related to the persons reading ability andwith the trailing edge of the terminal segment of the slot and theleading edge of the initial segment of the slot being disposed at arelatively lesser angle to the length axis of the line being scannedwhereby the terminal segment of the line is occluded and the initialsegment is unveiled at relatively more rapid rates than the rate of thecentral segment so that upon shifting of the aperture from beginning toend of the line and then shifting of the relative position of theaperture with regard to a succeeding line the transition from the endofeach line to the beginning of the succeeding line is more rapid and arelatively greater length of reading material is more rapidly exposed atthe beginning of the succeeding line to facilitate recognition.

14. In apparatus useful in improving a persons ability to view andcomprehend reading material in line-byline sequence of the type setforth in claim 13, the improvement which comprises providing means forvarying the rate of speed for shifting of the shutter mechanism so as tovary the rate of scanning and occluding the central and initial segmentsof the line to accommodate the viewing and recognition ability ofdifferent readers and for simultaneously proportionally varying the rateof occluding the terminal segment and the rate of unveiling of theinitial segment of each line.

15. In apparatus useful in improving a person s ability to view and tocomprehend reading material in line-byline sequence of the type havingmeans for separately exposing the lines in timed sequence, theimprovement which comprises:

a rotatable cylindrical shutter mechanism having an aperture forunveiling and occluding each line to view in segments in the directionof reading from the beginning of the line to the end of the line, saidaperture being shiftable with respect to each line upon rotation of theshutter so as to scan the line from beginning to end and being in theform of an elongated helical slot extending diametrically through thecylindrical shutter and being at least as long as the lines to bescanned and arranged so that when it is in operative position withrespect to a line it is disposed at an angle to the length axis of theline with the initial portion of the slot being disposed in a downwarddirection and the terminal portion being disposed in an upward directionwith respect to the line being scanned and with the leading and trailingedge of the central segment of the slot being disposed at relativelygreater angles to the length axis of the line being scanned than thehereinafter referred to edges of the slot so that the central segment ofeach line is scanned and occluded at a controlled rate of speed whichmay be related to the persons reading ability and with the trailing edgeof the terminal segment of the slot and the leading edge of the initialsegment of the slot being disposed at relatively lesser angles to thelength axis of the line being scanned whereby the terminal segment ofthe line is occluded and the initial segment is unveiled at relativelymore rapid rates than the rate of the central segment so that uponshifting of the aperture from beginning to end of the line and theshifting of the relative position of the aperture with respect to asucceeding line the transition from the end of each line to thebeginning of the succeeding line is more rapid and a relatively greaterlength of reading material is more rapidly exposed at the beginning ofthe succeeding line to facilitate recognition.

16. In apparatus useful in improving a persons ability to view andcomprehend reading material in line-byline sequence of the type setforth in claim 15 the improvement which comprises providing means forvarying the rate of rotation of the cylindrical shutter andcorrespondingly varying the rate of scanning and occluding of thecentral segment of the line so as to accommoate the viewing andrecognition ability of different readers and for simultaneouslyproportionally varying the rate of occluding the terminal segment andthe rate of unveiling of the initial segment of each line.

* i i i

1. In a method useful in improving a person''s ability to view and tocomprehend reading material in line-by-line sequence of the type inwhich the lines are separately exposed in timed sequence, theimprovement which comprises: unveiling and occluding each line to viewin segments in the direction of reading from the beginning of the lineto the end of the line with the central segment being scanned andoccluded at a controlled rate of speed which may be related to thepersons'' reading ability and with the initial segment being unveiled ata relatively more rapid rate than the rate of the central segmentwhereby a relatively greater length of reading material is more rapidlyexposed at the beginning of the succeeding line to facilitaterecognition.
 2. In a method useful in improving a person''s ability toview and comprehend reading material in line-by-line sequence of thetype set forth in claim 1 the improvement which comprises varying therate of scanning and occluding of the central segment so as toaccommodate the viewing and recognition ability of different readers andsimultaneously proportionally varying the rate of unveiling of theinitial segment.
 3. In a method useful in improving a person''s abilityto view and to comprehend reading material in line-by-line sequence ofthe type in which the lines are separately exposed in timed sequence,the imprOvement which comprises: unveiling and occluding each line toview in segments in the direction of reading from the beginning of theline to the end of the line with the central segment being scanned andoccluded at a controlled rate of speed which may be related to theperson''s reading ability and with the initial segment being unveiled ata relatively more rapid rate than the rate of the central segment andthe terminal segment of the line being occluded at a relatively morerapid rate than the rate of the central segment whereby the transitionfrom the end of each line to the beginning of the succeeding line ismore rapid and a relatively greater length of reading material israpidly exposed at the beginning of the next line to facilitaterecognition.
 4. In a method useful in improving a person''s ability toview and comprehend reading material in line-by-line sequence of thetype set forth in claim 3 the improvement which comprises varying therate of scanning and occluding of the central segment so as toaccommodate the viewing and recognition ability of different readers andsimultaneously proportionally varying the rate of occluding of theterminal segment and the rate of unveiling of the initial segment.
 5. Inapparatus useful in improving a person''s ability to view and tocomprehend reading material in line-by-line sequence of the type havingmeans for separately exposing the lines in timed sequence, theimprovement which comprises: a shutter mechanism for unveiling andoccluding each line to view in segments in the direction of reading fromthe beginning of the line to the end of the line said shutter mechanismhaving an aperture shiftable with respect to each line so as to scan theline from beginning to end and configured so that the central segment isscanned and occluded at a controlled rate of speed which may be relatedto the person''s reading ability and the initial segment is unveiling ata relatively more rapid rate than the rate of the central segment and arelatively greater length of reading material is more rapidly exposed atthe beginning of the succeeding line to facilitate recognition.
 6. Inapparatus useful in improving a person''s ability to view and comprehendreading material in line-by-line sequence of the type set forth in claim5 the improvement which comprises providing means for varying the rateof scanning and occluding the central segment so as to accommodate theviewing and recognition ability of different readers and forsimultaneously proportionally varying the rate of unveiling of theinitial segment.
 7. In apparatus useful in improving a person''s abilityto view and to comprehend reading material in line-by-line sequence ofthe type having means for separately exposing the lines in timedsequence, the improvement which comprises: a shutter mechanism forunveiling and occluding each line to view in segments in the directionof reading from the beginning of the line to the end of the line saidshutter mechanism having an aperture shiftable with respect to each lineso as to scan the line from beginning to end and configured so that thecentral segment is scanned and occluded at a controlled rate of speedwhich may be related to the person''s reading ability and the initialsegment is unveiled at a relatively more rapid rate than the rate of thecentral segment and the terminal segment of the line is occluded at arelatively more rapid rate than the rate of the central segment wherebythe transition from the end of each line to the beginning of thesucceeding line is more rapid and a relatively greater length of readingmaterial is more rapidly exposed at the beginning of the next line tofacilitate recognition.
 8. In apparatus useful in improving a person''sability to view and comprehend reading material in line-by-line sequenceof the type set forth in claim 7 the improvement which comprisesproviding means for varying the rate of scanning and occluding thecentral segment so as to accommodate the viewing and recognition abilityof different readers and for simultaneously proportionally varying therate of occluding the terminal segment and the rate of unveiling of theinitial segment.
 9. Apparatus useful in improving a person''s ability toview and comprehend reading material in line-by-line sequence of thetype set forth in claim 7 in which the lines of reading material to beexposed are mounted on a generally vertically disposed slide having arow of generally vertically disposed ratchet teeth and the apparatus isprovided with a generally vertically arranged opening to receive thesaid slide in alignment with the shutter, said apparatus also havingfeed mechanism including a pawl member for engaging said ratchet teethand having operating means synchronized with said shutter mechanism forreleasing and engaging successive teeth whereby the slide is feddownwardly by gravity with successive lines of reading material inalignment with the aperture.
 10. Apparatus useful in improving aperson''s ability to view and comprehend reading material inline-by-line sequence of the type set forth in claim 7 in which thelines of reading material to be unveiled are formed in first and secondparallel columns on a generally vertically disposed slide with thesecond column being in inverted relationship with respect to the firstcolumn, said slide having a first row of generally vertically disposedratchet teeth for the first column and a second generally verticallydisposed row of ratchet teeth for the second column which in turn isarranged in inverted relationship with respect to the first row, and thesaid apparatus is provided with a generally vertically arranged openingto receive the said slide in alignment with the shutter with the firstcolumn of reading material being in alignment with the aperture when theslide is in one vertical position and the second column being inalignment with the aperture when the slide is in an inverted position,said apparatus having feed mechanism including a pawl member forengaging the first row of ratchet teeth when the slide is in onevertical position and for engaging the second row of ratchet teeth whenthe slide is in inverted position and said apparatus having operatingmeans for said pawl synchronized with said shutter mechanism forreleasing and engaging successive teeth in said respective rows ofratchet teeth whereby the slide is fed downwardly by gravity withsuccessive lines of reading material in the respective columns inalignment with the aperture.
 11. In apparatus useful in improving aperson''s ability to view and to comprehend reading material inline-by-line sequence of the type having means for separately exposingthe lines in timed sequence, the improvement which comprises: a shuttermechanism for unveiling and occluding each line to view in segments inthe direction of reading from the beginning of the line to the end ofthe line said shutter mechanism being shiftable with respect to eachline so as to cause the aperture to scan the line from beginning to end,the said aperture being in the form of an elongated slot at least aslong as the lines to be scanned and being arranged so that when it is inoperative position it is disposed at an angle with respect to the lengthaxis of the line being scanned with the initial portion of the slotbeing disposed in a downward direction and the terminal portion in anupward direction with respect to the axis of the line and with theleading and trailing edge of the central segment of the slot beingdisposed at a relatively greater angle to the length axis of the linebeing scanned than the hereinafter referred to edges of the slot so thatthe central segment of the line is scanned and occluded at a controlledrate of speed which may be related to the person''s reading ability andwith the leading edge of the initial segment of the slot being disposedat a relatively lesser angle to the length axis of the line beingscanned whereby the initial segment is unveileD at a relatively morerapid rate than the rate of the central segment so that upon shifting ofthe apparatus from beginning to end of the line and then shifting of therelative position of the aperture with respect to a succeeding line arelatively greater length of reading material is more rapidly exposed atthe beginning of the succeeding line to facilitate recognition.
 12. Inapparatus useful in improving a person''s ability to view and comprehendreading material in line-by-line sequence of the type set forth in claim11, the improvement which comprises providing means for varying the rateof speed for shifting of the shutter mechanism so as to vary the rate ofscanning and occluding the central segment of the line to accommodatethe viewing and recognition ability of different readers and forsimultaneously proportionally varying the rate of unveiling of theinitial segment of each line.
 13. In apparatus useful in improving aperson''s ability to view and to comprehend reading material inline-by-line sequence of the type having means for separately exposingthe lines in timed sequence, the improvement which comprises: a shuttermechanism for unveiling and occluding each line to view in segments inthe direction of reading from the beginning of the line to the end ofthe line said shutter mechanism being shiftable with respect to eachline so as to cause the aperture to scan the line from beginning to end,the said aperture being in the form of an elongated slot at least aslong as the lines to be scanned and being arranged so that when it is inoperative position it is disposed at an angle with respect to the lengthaxis of the line being scanned with the initial portion of the slotbeing disposed in a downward direction and the terminal portion in anupward direction with respect to the axis of the line and with theleading and trailing edge of the central segment of the slot beingdisposed at a relatively greater angle to the length axis of the linebeing scanned than the hereinafter referred to edges of the slot so thatthe central segment of the line is scanned and occluded at a controlledrate of speed which may be related to the person''s reading ability andwith the trailing edge of the terminal segment of the slot and theleading edge of the initial segment of the slot being disposed at arelatively lesser angle to the length axis of the line being scannedwhereby the terminal segment of the line is occluded and the initialsegment is unveiled at relatively more rapid rates than the rate of thecentral segment so that upon shifting of the aperture from beginning toend of the line and then shifting of the relative position of theaperture with regard to a succeeding line the transition from the end ofeach line to the beginning of the succeeding line is more rapid and arelatively greater length of reading material is more rapidly exposed atthe beginning of the succeeding line to facilitate recognition.
 14. Inapparatus useful in improving a person''s ability to view and comprehendreading material in line-by-line sequence of the type set forth in claim13, the improvement which comprises providing means for varying the rateof speed for shifting of the shutter mechanism so as to vary the rate ofscanning and occluding the central and initial segments of the line toaccommodate the viewing and recognition ability of different readers andfor simultaneously proportionally varying the rate of occluding theterminal segment and the rate of unveiling of the initial segment ofeach line.
 15. In apparatus useful in improving a person''s ability toview and to comprehend reading material in line-by-line sequence of thetype having means for separately exposing the lines in timed sequence,the improvement which comprises: a rotatable cylindrical shuttermechanism having an aperture for unveiling and occluding each line toview in segments in the direction of reading from the beginning of theline to the end of the line, said aperture being Shiftable with respectto each line upon rotation of the shutter so as to scan the line frombeginning to end and being in the form of an elongated helical slotextending diametrically through the cylindrical shutter and being atleast as long as the lines to be scanned and arranged so that when it isin operative position with respect to a line it is disposed at an angleto the length axis of the line with the initial portion of the slotbeing disposed in a downward direction and the terminal portion beingdisposed in an upward direction with respect to the line being scannedand with the leading and trailing edge of the central segment of theslot being disposed at relatively greater angles to the length axis ofthe line being scanned than the hereinafter referred to edges of theslot so that the central segment of each line is scanned and occluded ata controlled rate of speed which may be related to the person''s readingability and with the trailing edge of the terminal segment of the slotand the leading edge of the initial segment of the slot being disposedat relatively lesser angles to the length axis of the line being scannedwhereby the terminal segment of the line is occluded and the initialsegment is unveiled at relatively more rapid rates than the rate of thecentral segment so that upon shifting of the aperture from beginning toend of the line and the shifting of the relative position of theaperture with respect to a succeeding line the transition from the endof each line to the beginning of the succeeding line is more rapid and arelatively greater length of reading material is more rapidly exposed atthe beginning of the succeeding line to facilitate recognition.
 16. Inapparatus useful in improving a person''s ability to view and comprehendreading material in line-by-line sequence of the type set forth in claim15 the improvement which comprises providing means for varying the rateof rotation of the cylindrical shutter and correspondingly varying therate of scanning and occluding of the central segment of the line so asto accommoate the viewing and recognition ability of different readersand for simultaneously proportionally varying the rate of occluding theterminal segment and the rate of unveiling of the initial segment ofeach line.